Parts of Doomed Russian Mars Probe to Hit Earth in January

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Russia's marooned Mars probe Phobos-Grunt, currently stuck in
orbit, is headed for a mid-January plunge into Earth's
atmosphere, and more than two dozen pieces of the huge spacecraft
could survive the fall, scientists say.

Current re-entry forecasts have the
Phobos-Grunt spacecraft falling Jan. 14 or 15, plus or minus
five days, according to space junk expert Heiner Klinkrad.

Klinkrad, head of the space debris office at the European Space
Agency's space operations center in Darmstadt, Germany, said
Russian scientists are hard at work assessing the re-entry
survivability of Phobos-Grunt, a spacecraft that tips the scale
at nearly 14 tons.

"They assume that about 20 to 30 fragments will reach ground with
an overall mass of less than 200 kilograms" - some 400 pounds of
leftover hardware, he said.

Phobos-Grunt launched into space Nov. 8 (Nov. 9 in Moscow),
but failed to transfer to an interplanetary trajectory. Its
mission was to land on Phobos, one of two moons circling the Red
Planet, snare samples and rocket them back to Earth in 2014.

A large part of Phobos-Grunt's massive bulk consists of the toxic
rocket fuel UDMH, short for unsymmetrical dimethylhydrazine and
nitrogen tetroxide. This propellant was reserved for
Phobos-Grunt's trip to Mars, and the spacecraft's failure to
leave Earth orbit means the fuel is still onboard and could start
spilling when the craft is 62 miles from the ground.

"The large aluminum propellant tank is likely to start leaking
near 100 kilometers altitude, release its UDMH and then largely
burn up," Klinkrad told SPACE.com.

According to the Russian federal space agency, Roscosmos, the
Phobos-Grunt probe is carrying roughly 7.5 metric tons of
hydrazine and nitrogen tetroxide.

Dealing with loaded tanks of toxic propellant in space has a
history. In February 2008, a disabled U.S. National
Reconnaissance Office spy satellite
was purposely destroyed just prior to re-entry using a
modified missile fired from the warship USS Lake Erie.

That satellite, USA-193, had a titanium tank carrying roughly 990
pounds (450 kilograms) of frozen hydrazine. The destruction of
the spacecraft was authorized due to the potential of the
titanium tank to survive re-entry intact, with its contents
posing a hazard to people on Earth.

If USA-193's tank had been made of a quicker-to-melt material
like aluminum, according to re-entry experts, taking out the
spysat would not have been necessary.

A matter of responsibility

ESA's Klinkrad said assessing the re-entry survivability of
Phobos-Grunt is normally left to the spacecraft's owners, "due to
their intimate knowledge of the spacecraft geometry, its mass
distribution and the materials involved."

According to NASA's Orbital Debris Program Office, a significant
amount of debris does not survive the severe heating that occurs
during re-entry. Components that do survive are most likely to
fall into the oceans or other bodies of water or onto sparsely
populated regions. No serious injury or significant property
damage from previous debris re-entries has been confirmed.

But one expert characterizes the Phobos-Grunt mishap as a major
setback for the space industry, both for the loss of science and
for the risks connected with an uncontrolled re-entry of a
massive, fully fueled spacecraft. [ Infographic:
Phobos-Grunt Mars Probe Explained ]

That's the view of Andrea Gini, founder and editor-in-chief of
the newly established Space Safety Magazine, published by the
International Association for Advancement of Space Safety and the
International Space Safety Foundation.

"While a lot is done today to ensure launch safety, safety of
operations, space debris tracking and avoidance, the issue of
re-entry is generally put on the back burner until it's too late
to actually do something about it," Gini told SPACE.com.

He said that the matter of falling debris is “too often
minimized” by authorities, who consider the risk of debris
hitting someone very low, given the distribution of the
population and the percentage of the Earth covered by water.

"I believe that uncontrolled re-entry is not a matter of risk but
a matter of responsibility,” Gini emphasized. "If an accident
will happen as a
consequence of falling debris, it will damage not only the
people or properties involved, but also the public perception of
the reliability of the space industry as a whole."

Sensitive matter

Russia's NPO Lavochkin was the main developer of the wayward
interplanetary probe.

Lev Zelenyi, director of the Space Research Institute in Moscow
and chairman of the Russian Academy of Sciences’ Solar System
Exploration Board, wrote in an open letter to Phobos-Grunt
colleagues Dec. 8: "Lavochkin Association specialists will
continue their attempts to establish connection with the
spacecraft and send commands until the very end of its existence.
We are working nevertheless on the issue of re-entry and
probability of where and which fragments may hit the ground (if
any)."

Zelenyi noted there is also "a sensitive matter" of the presence
of radioactive material, cobalt-57, in one of the scientific
instruments aboard Phobos-Grunt. He added, however, that the
amount contained in the device is less than 10 micrograms and no
significant problems are anticipated.

The apparatus containing the cobalt-57 is the miniaturized
Mössbauer Spectrometer — MIMOS II — developed by the Institute
for Inorganic and Analytical Chemistry at the University of Mainz
in Germany. This instrument, a modified version of gear onboard
NASA's
Mars rovers Spirit and Opportunity, was to examine the
chemical composition of rocks on Phobos. MIMOS II is roughly the
size of your hand and is mounted on a robotic arm of the landing
module that was to plop down on Phobos. The device works by
subjecting a sample to gamma radiation and measuring the
gamma-rays that are absorbed and re-emitted by the sample.

Built to beat the heat

One likely bit of spacecraft hardware that seems certain to
survive the fall is the Phobos-Grunt descent space vehicle: the
probe’s sample return capsule, which has a thermal protection
coating.

If all had gone well with the mission, this nose-cone-shaped
container would have hauled back to Earth bits of Phobos for
detailed scientific analysis. The descent space vehicle was built
to survive the heat of re-entry and to fall without parachute
into the Sary Shagan missile test range in Kazakhstan.

This capsule contains the Living Interplanetary Flight Experiment
(LIFE) designed and built by the Planetary Society, apublic space
organization headquartered in Pasadena, Calif.

According to the Planetary Society’s website, LIFE was devised to
assess whether organisms can survive for years in deep space.
LIFE carries selected organisms to "test one aspect of
transpermia, the hypothesis that life could survive space travel
if protected inside rocks blasted by impact off one planet to
land on another."

The microbes selected and carried by LIFE are not dangerous to
humans, the website added.

Leonard David has been reporting on the space industry for
more than five decades. He is a winner of this year's National
Space Club Press Award and a past editor-in-chief of the National
Space Society's Ad Astra and Space World magazines. He has
written for SPACE.com since 1999.